1. Field of the Invention
This invention relates to a stationary blade ring of an axial compressor, such as a gas turbine compressor, the stationary blade ring being designed to improve reliability and performance of a compressor by achieving built-up stationary blades.
2. Description of the Related Art
FIGS. 7(a) and 7(b) are explanation drawings of a compressor stationary blade ring of a conventional gas turbine, FIG. 7(a) being a sectional view, and FIG. 7(b) a view taken in the direction of an arrow C in FIG. 7(a). In the drawings, the numeral 100 denotes a stationary blade of a compressor, and the numeral 101 denotes an outer shroud for the stationary blade. The outer shroud 101 is built into a compressor casing 102. The numeral 103 denotes an inner shroud. The stationary blade 100 is fixed by fillet welding to the outer shroud 101 and the inner shroud 103 at tenon portions (protrusions) 100a and 100b, respectively. The numerals 104a, 104b are seal arms for the inner shroud 103 which oppose the seal surface of a rotor 105 for preventing leakage of compressed air (see Japanese Unexamined Patent Publication No. 1998-317910).
In the above-described structure, the stationary blade 100 is fixed by welding to the inner shroud 103 and the outer shroud 101. A plurality of the stationary blades 100 are arranged circumferentially to constitute a stationary blade ring which is divided into two parts on the entire circumference. A plurality of such stationary blade rings are mounted in the axial direction, and moving blades are rotated between these stationary blade rings to form gas turbine operating air.
With the above-described stationary blade ring as the earlier technology, however, the stationary blade 100 and the inner and outer shrouds 103, 101 are bound together at the tenon portions 100a, 100b. In welding, a notch defect may occur in the bottom of a welded overlay. This tendency is strong with fillet welding of this example, where there is a possibility for the occurrence of cracking starting in the fillet weld zones. The seal arms 104a, 104b are also bound to the inner shroud 103 by fillet welding, thus posing the same possibility. Under these circumstances, a further improvement in the life of the compressor stationary blade has been demanded.
Furthermore, the stationary blade 100 and the inner and outer shrouds 103, 101 are fixed to each other by fillet welding, and they are constructed metallurgically integrally. This has caused the disadvantage that a damping effect is low in response to vibrations of the blade. If the blade is thinned, there will be overstress, presenting an impediment to an improvement in the performance of the compressor ascribed to the thin-walled blade.
The present invention has been accomplished in light of the above-described problems with the earlier technology. It is an object of the invention to provide a stationary blade ring of a compressor, the stationary blade ring being composed of built-up stationary blades, which remove the notch at the junction between the shroud and the blade, and improve damping responsive to vibrations to render it possible to thin an airfoil, thereby achieving improvements in the reliability and performance of an axial compressor including a gas turbine compressor.